The present invention relates to switching amplifiers and more specifically to techniques which enable inductorless switching amplifier architectures. Still more specifically, some embodiments of the invention relate to such architectures which employ sigma-delta modulation.
Switching amplifier and regulator architectures typically employ output filters to remove switching power from the output signal before it is applied to the load. That is, such architectures often switch at frequencies which are much higher than the frequency of interest. For example, in audio applications, switching amplifiers typically switch at 800 kHz or above as compared to the upper end of the frequency band of interest, i.e., 20 kHz. Without a suitable output filter, the energy of the switching frequency would be dissipated in the load. However as is well known, such output filters typically include external inductors and capacitors which are expensive and consume undesirable amounts of space.
Some solutions have been proposed in which output filters may be eliminated by reducing the switching power dissipated in the load. However, these solutions have been limited to pulse-width modulation applications in which the output frequency (and therefore the beginning of each successive pulse) is fixed. None of these solutions are suitable for switching topologies in which the output frequency varies, e.g., sigma-delta modulators.
It is therefore desirable to provide additional switching amplifier and regulator architectures which do not require output filters.